1. Field of the Invention
The invention relates to an array microphone system, and more particularly to an array microphone system including two omni-directional microphones to receive sound in a cone-shaped beam.
2. Description of the Related Art
A microphone array is capable of clearly receiving sound from a particular direction while excluding surrounding noise, and is often applied in high-quality audio recorders or communications devices.
FIG. 1 depicts a conventional microphone array 70 including a uni-directional microphone (main microphone) 710 and an omni-directional microphone (reference microphone) 720. A cone-shaped beam 730 is defined in front of the uni-directional microphone 710. The microphone array 70 utilizes the sensitivity difference between the uni-directional microphone 710 and the omni-directional microphone 720 to exclude surrounding noise (i.e. the sound outside the beam 730).
The microphone array 70 functions very well. However, the uni-directional microphone 710 included in the microphone array 70 has the problems of being difficult to manufacture because of its design and high costs.
FIG. 2 depicts another conventional microphone array 80 including two omni-directional microphones 810 and 820. A pie-shaped beam 830 is defined at the front and the rear of the microphone array 80. The microphone array 80 utilizes the phase delay of the sound received by the two omni-directional microphones 810 and 820 to exclude surrounding noise (i.e. the sound outside the beam 830).
The microphone array 80 has no uni-directional microphones and thus, does not have the accompanying problems of uni-directional microphones. However, sounds coming from the rear of the microphone array 80 can not be excluded due to the pie-shaped beam 830. Thus, limiting actual application of the microphone array 80 to less than that of the microphone array 70.